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Herein, a graphene nanosheet (GNS)/nickel‐based superalloy matrix composite with certain orientated GNS is fabricated via the powder metallurgy method. The solution mixing method is applied to obtain a superalloy powder with embedded GNS. Well‐arranged GNS in the composite can be obtained by subsequent hot isostatic pressing, isothermal extrusion, and isothermal forging, which lead to anisotropic mechanical properties with ductility in radial and tangential direction better than in axial directions. Consequently, a moderate strength improvement (111–116 MPa at 0.1 wt% GNS) is achieved in the composite without losing its ductility in radial and tangential direction, while the elongation reduces from 21.0% to 15.7% in the axial direction. When the loads are perpendicular and parallel to the GNS alignment direction, respectively, two different interface failure modes of "GNS interlayer delamination" and "GNS pulled out" are caused, which result in the anisotropic mechanical behavior. This finding may provide a new perception in informing the strengthening behaviors of GNS‐reinforced FGH96 composite. [ABSTRACT FROM AUTHOR]

An X-ray amorphous phase is frequently present at the early stage of calcium phosphate crystallization, and the relevant solution chemistry is essential for understanding the mechanism of reaction. Here, we report a quantitative study of a series of reaction systems at pseudo-equilibrium states. We determined the composition of solutions and the quantities of the precipitate samples, and characterized the long- and short-range order of the precipitate using X-ray diffraction and synchrotron X-ray absorption near-edge structure spectroscopy, respectively. We found that, in a particle with multiple structural units, only a fraction of the units was able to reach pseudo-equilibrium with the solution composition, which represents the average number of surficial clusters per unit. These findings enabled us to propose a general form of the equilibrium constant equation. The equation fits the pseudo-equilibrium data well, and it converts to the "solubility product (Ksp)" and the conventional "reaction quotient" in two limit cases, respectively. Further, using a cube model, we derived a "particle equation" that reveals the connection between the particle structure and the form of equilibrium constant equation. The dependency of the form of pseudo-equilibrium equation on the structure and size of the precipitate reveals a fundamental relation in chemistry, and its applicability remains to be examined in other reaction systems, such as those involving nanocrystals and porous materials. [ABSTRACT FROM AUTHOR]

The co-exposure of antibiotics has important effects on antibiotic resistance genes (ARGs) and microbial community aggregation in wastewater treatment plants (WWTPs). However, it is unclear whether differences in historical antibiotic exposure stress can determine responses of microbes and ARGs to combined antibiotics. By selecting a high concentration (30 mg·L -1 ) of sulfamethoxazole (SMX) and trimethoprim (TMP) as historical exposure stress conditions, the effects of SMX and TMP-combined pollution on ARGs, bacterial communities, and their interactions were explored in short-term experiments. Based on high-throughput quantitative PCR, a total of 13 ARGs were detected, and the absolute abundance was 2.21-5.42 copies·μL -1 (logarithm, DNA, the same below). Among them, sul2, ermB, mefA , and tetM-01 were the main subtypes in the samples, and the absolute abundance was between 2.95 and 5.40 copies·μL -1 . The combined contamination of SMX and TMP could cause the enrichment of ARGs and mobile genetic elements (MGEs); however, their effects on each subtype were different, and the historical legacy effect of SMX was higher than that of TMP. Under the different exposure histories, the co-occurrence and co-exclusion patterns existed between ARGs. Moreover, MGEs (especially intI-1 ) were significantly correlated with sulfonamides ( sul1 and sul2 ), tetracyclines[ tet(32) ], and macrolide-lincosamide-streptogramin (MLSB) resistance genes ( ermB ). Based on the full-scale classification of microorganisms, it was found that the microbial community structure of various groups responded differently to combined pollution, and the conditionally abundant taxa (CAT) were obviously enriched. Thauera, Pseudoxanthomonas, and Paracoccus were the dominant resistant bacterial genera. Furthermore, a total of 31 potential hosts of ARGs were identified with network analysis, which were dominated with conditionally rare taxa (CRT). Particularly, Candidatus_Alysiosphaera and Fusibacter were positively correlated with most of the ARGs, being the common protentional hosts. Importantly, some rare genera (RT, Variibacter, Aeromonas, Cloacibacterium , etc.) were potential hosts of transposon IS613 , which played an important role in the proliferation and spread of ARGs. In conclusion, this study revealed the legacy effects of historical antibiotic stress on ARGs and their hosts, which could provide new ideas and theoretical basis for reducing ARGs pollution in WWTPs.

Objective: To investigate the influence of intranasal instilling titanium dioxide (TiO2) nanoparticles on monoaminergic neurotransmitters at different-time exposure., Methods: CD female mice were intranasally instilled three different-sized (25 nm, 80 nm and 155 nm) TiO, suspension every other day in a dose of 50 mg/kg body weight. The control group was instilled the same volume of Milli-Q water. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to analyze the titanium contents in murine brain after exposure to TiO2 particles 2 days, 10 days, 20 days and 30 days. The monoaminergic neurotransmitters such as norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), 5-hydroxyindole acetic acid (5-HIAA), 3, 4-dihydroxyphenylacetic acid (DOPAC), and homovanillic (HVA), were determined by reversed-phase high performance liquid chromatography (RP-HPLC) with electrochemical detector., Results: After exposure to TiO, nanoparticles 10 days, the titanium contents in murine brain were increased, the titanium content in the 25 nm group was up to (1059.3 +/- 293.5) ng/g. In 20 days, the titanium content decreased slowly with the metabolism of titanium in vivo, but it kept at a high level, the content decreased to (654.7 +/- 269.2) ng/g in the 25 nm group. After exposure to TiO2 nanoparticles 30 days, the titanium contents had no obviously change. Because of the accumulation of TiO, in the brain, the contents of NE and 5-HT increased significantly after exposure to 80 nm and 155 nm TiO, nanoparticles 20 days, while the decreased contents of DA, DOPAC, HVA and 5-HIAA were observed., Conclusion: The inhaled TiO2 nanoparticles could be translocated to and deposited in murine brain after absorbing by nasal mucosa, and further influence the releases and metabolisms of monoaminergic neurotransmitters in brain.

The analytical method for the determination of total mercury and methylmercury in biological samples was studied using ultrasonic-assisted solvent extraction coupled with inductively coupled plasma-mass spectrometry. Various extraction conditions like solvent types and concentrations, different assisted methods, and ultrasonic radiation time were optimized. Samples were digested with 6 mol x L(-1) HCl, ultrasonicated for 2 hours, extracted by organic solvent, then back-extracted by water and directly measured after dilution. With the optimized method, the total mercury and methylmercury were simultaneously measured. The detection limit was 0. 01 ng x mL(-1) , the relative standard deviation (RSD) was 3. 44%, the linearity of calibration curve of mercury was in the concentrations of 0-50 ng x m(L-1), and the recovery of mercury given by standard addition method was 80%-97%. Mercury in five different biological standard reference materials was determined by the described method. The experimental results were in good agreement with the certified values. The proposed method takes the advantage of ultrasonic-assisted extraction, micro-solvent extraction, and ICP-MS, which is especially suitable for the analysis of mercury in different biological samples.

In the environment and living organisms, limited concentrations and complexity of selenium compounds constitute challenges to the analytical techniques. Since their biological activities are dependent on their chemical states and structure, the key issue lies in the selective determination of the particular species of selenium, which is beneficial to clearly understanding its biochemical roles in metabolism, physiology, toxicology, nutrition, and clinical chemistry. For these purposes, the advanced analytical techniques are greatly indispensable. In the present paper, the current status and development trends in the speciation analysis of selenium by hyphenated techniques is selectively reviewed with the emphasis on the coupling of electrophoretic or chromatographic separation with atomic spectroscopy and mass spectrometry, which render element-selective detection and identification of selenium compounds.

Objective: The present paper makes an attempt to evaluate the risk of mercury exposure to human by analyzing the total mercury and methylmercury concentrations of four commercially important freshwater fish species in Beijing market., Methods: Fish samples of common carp, grass carp, bighead carp, and snakehead were purchased from Beijing market. Then their muscle, liver and gills were taken out. The total mercury and methylmercury concentrations were determined using ultrasonic-assisted solvent extraction coupled with inductively coupled plasma-mass spectrometry. Samples were digested with 6mol/L HCl and sonicated for 2 hours. Subsequently, some aliquots were directly diluted for determination of total mercury concentrations; the remained extracts were extracted with CH2 C12 , and then back extracted with H20 for determination of methylmercury concentrations. To evaluate the validity of the method, the standard materials of DORM-2 and DOLT-3 were also measured., Results: According to the concentrations oof total mercury and methylmercury in the muscles, an order was obtained as: snakehead > bighead carp > grass carp > common carp, which showed that the accumulation of mercury in fish was closely related to food chain. Methylmercury were about 80% of the total mercury, whereas there was a positive relationship between total mercury and methylmercury. The mercury distributions in the bighead carp and snakehead fish showed that the order of mercury concentrations was: muscle > liver > gill, the ratio of methylmercury to total mercury was: muscle > gill > liver. Methylmercury was mainly accumulated in the muscle of fish., Conclusion: mercury concentrations of the four fishes in Beijing markets were all below the standard level according to the National Standard of China, therefore, it is safe to human health.